2. LA complications Flashcards
List the 6 systemic complications
- Psychogenic
- Overdose
- Allergy
- Drug interaction
- Vasoconstriction
- Medical conditions
What is the difference between a faint and a LA over dose?
A faint is a vaso-vagal response, where there is a sudden drop in heart rate and blood pressure. Usally triggered by percieved stress of patients. Non-toxic, usually recover in short time.
(other psychogenic systemic complications includes: nausea, anxiety, restlessness, perspiration, palpatation)
LA overdose is toxic, usually related to the age, weight, medical conditions, genetics and drug interations.
What are the maximum dose and concentration of the following drugs:
- lignocain + adrenaline
- prilocain + felypressin
- bupivicain + adrenaline
- articain + adrenaline
- mepivicain +/- adrenaline
- lignocain + adrenaline, 7mg/kg, 2%
- priolocain + felypressin, 9mg/kg, 2%
- bupivicain + adrenaline 2mg/kg
- long duration of onset (5min)
- long duration of action (hours)
- for post-operative pain
- articain+ adrenaline, 7mg/kg, 4%
- good bone penetration
- mepivicain +/- adrenaline 7mg/kg, 2%
- with/without adenaline
What is the maximum number of injections of articain (7mg/kg, 4%) of cartridge 2.2ml can you give to an 55kg female before overdose?
55kg x 7mg/kg = 385mg
4% = 0.04g/ml = 40mg/ml
40mg/ml x 2.2ml/cartridge = 88mg/cartrdge
385mg ÷ 88mg/cartrdge =4.375 cartridges ≈ 4 cartridges
Maximum dosage is related to age because?
Younger patients have lighter weight while older patients are prone to medical conditions, medications, and worse metabolisms (renal/hepatic diseases)
Contraindications and adverse effect for atypical pseudocholinesterase patients are?
Avoid procain (ester-derived drug)
usually previous history of problems with GA, muscle relaxant
usually self-reported by patients
benzocain in mouth rinses contraindicated
describe High blood concentration related overdose
- LA are generally vasodilators, thus vasoconstrictors are added to slow clearance from local region and uptake into CVS
- high tissue concentration leads to high blood concentratoin (overdose)
- avoid injecting intravascularly (aspirate to check)
- should inject slowly
Why do we avoid injecting into inflammed areas
- painful
- highly vascular
- risk of infection
- low pH which obstruct LA dissociation, lowered function
- LA’s pH = 7.6-9
- health tissue pH = 7.4
- inflammed tissue pH = 5-6
- thus delay or no effect of LA
- should consider nerve block
Describe the signs and symptomes of Excitation phase of overdose
(cortical and medullary signs)
- depression of inhibitory centres
- cortical signs
- restlessness/aggitation
- slurred speech
- localised muscular twitching/convulsions
- dizziness
- difficulty focusing eyes
- circumoral numbness (pertaining to the area of the face around the mouth)
- medullary signs
- increased heart rate
- increased blood pressure
- increased respiratory rate and depth
(check radial pulse to differentiate between vaso-vagal respons; tachycardia=overdose bradycardia=faint
Describe the signs and symptomes of Depression phase of overdose
(cortical and medullary signs)
progresses from excitation phase
- cortical signs (brain goes numb)
- lethargy
- drowsiness
- unresponsiveness
- muscular weakness
- medullary signs
- decreased HR, BP, breath rate and depth
- potentially leading to coma and death
How to manage overdose
- stop treatment
- recovery position
- oxygen support
- reassure patient
- monitor vital signs (respiratory rate can best guide)
IF RESPIRATORY ARREST, call ambulance and CPR
True/False
Allergy is dose dependent
False
hypersensitivity is not dose dependent
- ester-linked allergy are common (procain, benzocain)
- amide-linked allergy is rare
- may be allergic to preservatives, methylparaben (not common these day, no longer added)
What are the clinical presentations of allergy
fever
urticaria
angiodema
dematitis
photosensitivity
anaphylaxis
When patients are taking (name 6 substances) ______, we should ________(reduce/increase) dosage of LA
- narcotics
- antihistamines
- benzodiazepines
- barbiturates (CNS depressants)
- nitrous oxide
- alcohol
- talk to MD and document
- these drug interactions may lead to CNS and CVS deoression
we should REDUCE THE DOSAGE
Why do we add adrenaline/vasoconstrictors to LA?
- reduce necessary dosage, thus reduce toxic dose
- confine LA to area of injection
- reduces bleeding into surgical field
commonly adrenline and felypressin
